Related Field
The present invention relates to an extended nip roll for use in a nip through which a fibrous web is to be passed.
Description of Related Art
It is previously known that an extended nip for treatment and/or processing of a fibrous web can be formed between an extended nip roll and a counter element and where the counter element is normally (but not necessarily) a counter roll. Extended nip rolls have been disclosed in several patents, for example in U.S. Pat. No. 7,527,708, U.S. Pat. No. 6,383,338, U.S. Pat. No. 6,017,422, U.S. Pat. No. 6,010,443, U.S. Pat. No. 6,036,820 and U.S. Pat. No. 5,925,219. Such extended nip devices are typically used for dewatering of wet paper webs in a paper machine but may also be used for other purposes than dewatering. For example, it is known that such devices may also be used for calendering and an example of this is disclosed in U.S. Pat. No. 6,158,335. Extended nip rolls may also be used for other treatment or processing of paper webs, for example in coating devices. In extended nip rolls, a press body is used which is often in the form of a rigid metal shoe (e.g. a shoe of steel or aluminum) and which has a surface which is concave and intended to cooperate with a convex counter element such as a roll to form a nip. Extended nip rolls using such a rigid and concave shoe are usually referred to as “shoe rolls”. Instead of a concave metal shoe, an extended nip roll may also use a press body which is flexible and capable of adapting its shape to the shape of a counter element. An example of such a device is disclosed in for example U.S. Pat. No. 7,527,708.
In extended nip rolls with a press body, the press body is looped by a tubular flexible jacket and the axial ends of the tubular flexible jacket are usually attached to end walls such that an enclosed space is created. It is desirable that, during operation, the tubular flexible jacket does not sag or flatter. To prevent the tubular flexible jacket from sagging or fluttering, the enclosed space can be filled with pressurized air. Feeding pressurized air to the inside of the tubular flexible jacket helps the jacket to keep its shape. To provide further support for the flexible tubular jacket, the extended nip roll may be provided with an internal support ledge that is arranged to support the flexible tubular jacket. U.S. Pat. No. 5,520,782 discloses embodiments where the jacket of a shoe press may be supported by radially movable support ledges 31, 38 (see for example FIG. 5 or FIG. 6 of U.S. Pat. No. 5,520,782). A support element such as a support ledge may be helpful in making the jacket keep its shape. The object of the present invention is to provide an improved supporting device for the tubular jacket of an extended nip roll.